1. Field of Invention
This invention relates to a keyless lockable security device, specifically a high-security seal, or seal lock which secures the access doors of rail cars, trailer trucks, and cargo containers.
2. DESCRIPTION OF PRIOR ART
The access doors of railroad cars, trailer trucks, and cargo containers are customarily closed with a seal which is installed on the hasp of the access door. The primary function of the seal is to indicate if the doors had been opened by unauthorized personnel. Once secured, the seal should provide a permanent closure which cannot be opened without resulting in significant visible damage and the destruction of the seal device, which prevents its reuse. If the seal can be opened, by any means whatsoever, without resulting in visible damage and the destruction of the seal, thereby allowing the seal to be reused and appear intact, it has failed to perform its primary function.
Various forms of seals have been used in the past on the access doors of trucks, rail cars, and cargo containers. Conventional seals frequently have consisted of a metal tape or a plastic band with a single securement member, when engaged therewith, it is impossible to remove the seal without the destruction of the securement member or the tape, or band. The prime purpose of these conventional seals has not been to secure the access doors from unauthorized entry, but for the purpose of indicating that such unauthorized access had been made.
In recent years the increase in thefts from trailer trucks, rail cars, and cargo containers has resulted in a new type of seal which embodies all the characteristics of a conventional seal in addition to providing increased strength and security by being constructed of heavier and more substantial materials, often times requiring the use of special tools to effect removal. These new types of seals have been rightly termed high-security seals, or seal locks.
Seal locks are a more practical solution than padlocks. It has been impractical to lock containers with padlocks, because of the problem of transferring keys or combinations. In addition, the complex mechanical construction of padlocks results in them being an expensive security alternative to seal locks. Once a seal lock is engaged, it is intended that it cannot be disengaged without destroying the seal, thereby preventing its reuse. Thus the single use of the seal requires that the seal lock be low cost yet effectively provide a high level of security protection.
Heretofore several types of seal locks have been proposed. One type of seal lock construction requires the assembly of two separate pieces. Seal locks of this type are known from U.S. Pat. Nos. 4,690,443 to Brammall (1987), 4,280,726 to McCoag (1981), 4,075,742 to Remark (1978), 3,980,337 to Moberg & Lundberg (1976), 3,994,521 to Van Gompel (1976), 3,945,671 to Gerlach (1976), 3,937,507 to McCoag (1976), and 3,730,578 to Gerlach (1973). When a seal lock is constructed with two separate pieces, the loss of either piece, prior to use, renders the seal useless. Thus a person using this type of seal must maintain a careful inventory and count of both pieces to avoid misplacing one portion of the seal lock. This is an inconvenient and difficult task to perform while operating a busy cargo terminal facility, and when seal lock components are bulk packaged in cartons, the user would not be aware of any shortages of a given component until the last seals from the carton were used.
Several embodiments of the above mentioned prior art utilize a bolt member as one of the components of the seal lock. The typical hole diameter of the access door hasp limits the diameter of the shaft of the bolt to a maximum of 3/8" diameter. Such bolt member is typically a cold-headed part. The process of cold-heading has certain physical and economic limitations regarding the maximum diameter head that can be achieved when a 3/8" diameter shaft is used. In practice this manufacturing consideration limits the head diameter of the bolt member to 3/4".
In many rail cars, truck trailers, and cargo containers the hole diameter of the locking hasp of the access doors is larger than 3/4". This increased hole diameter is as a result of years of wear, manufacturing variations, or damage. In either case, a seal lock having a bolt member with a 3/4" diameter head is useless on any hasp having a hole diameter of 3/4" or larger. Padlock type seal locks recognize this limitaion and utilize a "U" shaped shackle as shown on U.S. Pat. No. 3,937,507 to McCoag (1976).
High security seals, or seal locks, derive their strength by utilizing heavier metal components in their construction. The use of stronger materials increases the difficulty in breaking the seal lock open. When an attempt is made to open a seal lock by force, it is important that the seal perform its primary function, as stated above, and be destroyed by such an attempt. However, the same heavier metal components which increase the difficulty of breaking the seal open, also transfer most of the forces being applied to the seal, directly to the locking mechanism. My testing indicates that the relative strength of the locking mechanisms of seal locks is significantly less than the strength of the other components of the seal lock. Therefore, when sufficient forces are applied to the seal locks that have been previously proposed, the locking mechanisms release before any visible damage is done to the seal lock, thereby allowing the seal lock to be reused without apparent indications of tampering.
Seal locks previously proposed require that one cut be made to remove the seal from the access door hasp. Whether that cut be made by a bolt cutter in the case of a seal lock using a bolt member or shackle, or a cable cutter in the case of a seal lock using a length of wire rope or cable. A seal lock which can be removed by means of a single cut is less secure than a seal which requires more than one cut to effect removal.
The present invention is designed toward overcoming one or more of the problems set forth above.